IntroductionNeurological procedures can lead to significant postoperative deficits. It is important for doctors to evaluate nervous system function during surgery so that any deficits can be corrected before they become permanent. The oldest method for evaluating spinal cord function is the Stagnara awakening test, in which patients are awakened in the middle of surgery to evaluate motor function (1). Once the patient's neurological status has been assessed, the patient would be re-anesthetized and the surgery would resume. The arousal test is limited in that it provides only a brief assessment of motor function. It fails to detect ischemia and sensory function(2). Now, intraoperative neurophysiological monitoring with motor evoked potentials (MEPs), somatosensory evoked potentials (SEPs), electromyography (EMG), electrocorticography (ECoG), and cortical mapping has become the new standard of care. It allows doctors to examine nervous system function without waking the patient. It has become an essential intraoperative tool to improve safety in surgical procedures and help minimize postoperative deficits. It allowed surgeons to accept high-risk patients who would otherwise have been denied surgery. There are many intraoperative monitoring modalities used to evaluate different parts of the brain, spinal cord, and peripheral nervous system. The strength of each modality can compensate for the limitations of other monitoring modalities and, when combined together, provide a complete picture of the complex function of the spinal cord. Motor Evoked Potentials (MEPs) Motor evoked potentials (MEPs) are widely used to diagnose and evaluate the functional integrity of the descending motor pathway… half of paper… to evaluate postoperative sensory function. It is important to note some strengths and limitations of SEPs. The strengths of SEPs are that they allow continuous monitoring, have excellent specificity, and can be used with neuromuscular blocking agents (11). One limitation of SEPs is that it requires temporal summation of neural signals entering the spinal cord. The recorded data is based on calculated averages, so it may take several minutes after an acute insult to appear in the data. Studies have shown that the average delay of SEPs is 16 minutes after MEPs and that SEPs can be delayed up to 33 minutes(19). Other limitations of SEPs are that it does not directly monitor the corticospinal tract, has low sensitivity for motor deficits, and its recording may remain unchanged in patients with anterior spinal artery injury(11).